Modal Verbs

Modal Verbs

1. For obligation

   • We can use have to + infinitive, must + infinitive and should + infinitive to express obligation (something you have to do).
     • Be careful about the difference between mustn't and don't have to! Mustn't means it's not allowed, or it's a bad idea
     • Don't have to means you don't need to do something, but it's fine if you want to do it

2. Of Necessity

   • Must is the strongest and most serious modal verb of the three and is most common in writing. It is unusual to use “must” in questions.
     • Have got to is most common in informal speech. It is not used in questions.
       • Have to is the most commonly used modal of obligation. It is useful for forming questions and negatives.
         • The subject and verb must agree for he/she/it subjects AND the question form requires “Do/Does/Did”.

3. For Prohibition

   • These situations are the opposite of giving permission.
     • The modal verbs used are May and Can. They are used as negatives: Can’t Must not May not

4. To express criticism

   • Present and future Can, could, might and should/shouldn't + infinitive are used to express criticism or disapproval with reference to present or future time
     • Past Could, might and should/shouldn't + perfect infinitive are used to express criticism or disapproval with reference to past time

5. For Possibility

   • We can use modal verbs to talk about possibility or to express uncertainty in the present and future using modal verbs may, might and could.

6. For Advice

   • should ought to had better
     • English speakers use the modal verbs “should,” “ought to” and “had better” to express that they think something is a good (or a bad) idea. “Should” is the most common way to give advice.

7. Deductions

   • guessing if something is true using the available information. The modal verb we choose shows how certain we are about the possibility. This page focuses on making deductions about the present or future.
     • must We use must when we feel sure that something is true or it's the only realistic possibility.
     • might, may, could We use might, may or could to say that we think something is possible but we're not sure.
     • can't We use can't when we feel sure that something is not possible.

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